The passive seat belt apparatus of the door mounting type in which the attachment and release of the belt are automatically executed in accordance with the opening/closure of the door of a vehicle has an advantage in that the seat belt is semiforcedly attached without needing any troublesome operation and the attachment of the seat belt is recommended.
As such a kind of seat belt apparatus, there is a known apparatus in which a retractor is attached in the lower rear portion open side of the door, wherein the retractor has a wind-out rotation emergency locking function such that, ordinarily, a belt edge portion is elastically wound and a proper tension is applied to the belt, and the belt can be easily pulled out as necessary, and when a sudden acceleration or deceleration occurs in the vehicle and when the belt is suddenly pulled out such as in the case of a collision or the like, the acceleration/deceleration of the vehicle and the pulling-out of the belt are sensed and the belt is locked. In the case of a structure in which the retractor is installed in the door, there is concern that the belt may be locked when the door is suddenly opened due to the pulling-out speed of the belt and the acceleration/deceleration of the door itself when the door is opened or closed. Therefore, for instance, as shown in the invention disclosed in JP-B-57-33186, for example, there is known a structure such that the emergency locking function is made operative (by the retractor and a door switch which is attached near the lower portion of a center pillar of the vehicle) only when the door is closed, and when the door is open, the emergency locking function of the belt is cancelled, thereby preventing locking of the belt. Generally, the emergency locking function is cancelled by using a belt lock cancelling solenoid provided in the retractor.
In the apparatus disclosed in JP-B-57-33186 and other conventional examples, it is surely possible to effectively avoid unnecessary locking of the belt when the door is open. However, in the emergency lock of the belt, "LOCK" and "UNLOCK" are ordinarily controlled in accordance with a value of an output of a G sensor (acceleration sensor) provided in the retractor. Therefore, there is a case where the belt is locked by an instantaneous high shock value when the door is closed. Thus, there is an inconvenience in that the belt is locked before the passenger fastens the belt.
Accordingly, it is an object of the invention to provide a control apparatus of a passive seat belt which can effectively avoid unnecessary actuation of the emergency locking function of the belt due to a shock when the vehicle door is closed.
The door switch in the above conventional examples is, in many cases, also commonly used to switch a courtesy light. However, the structure of the door switch is frequently such that, when the door is closed, the movable contact is pressed away from the fixed contact against an original position return spring, thereby opening the switch. That is, the switch senses the pressing force of the door. Therefore, when the door is closed and retained to the vehicle body, but not fully positively latched thereto, the ON/OFF state of the door switch is obscure and, in many cases, the door switch is set to ON, indicating the door is open. Therefore, although in many cases a main courtesy light switch is turned OFF in the daytime, if the driver intends to drive the vehicle with the door in such a closed but incompletely latched state, there is an inconvenience in that the belt lock cancelling solenoid operates, cancelling the emergency locking function of the belt.
It is therefore another object of the present invention to provide a passive seat belt apparatus which can effectively prevent cancellation of the emergency locking function of the belt when the door is closed but not completely latched.
Also in the above conventional examples, there is used a structure in which the belt lock function is prevented by driving the belt lock cancelling solenoid through a relay whose contact is closed by the turn-on of the door switch or a controller which detects the ON signal of the door switch. Therefore, there are inconveniences when the relay or controller malfunctions due to noises or the like from the outside, and even in the case where the belt locking function must not inherently be cancelled, the belt lock cancelling solenoid operates.
It is therefore another object of the invention to provide a control apparatus of a passive seat belt in which it is possible to effectively prevent the belt lock cancelling solenoid from erroneously operating in response to noises and the like from the outside.
In an embodiment of the present invention, there is provided a control apparatus having a belt lock cancelling solenoid to cancel a wind-out rotation emergency stop function of a retractor having the wind-out rotation emergency stop function for sensing an acceleration/deceleration of the vehicle and a pulling-out speed of the belt and for locking the belt; a door switch to detect the opening/closure of the door; and a main control unit for making the belt lock cancelling solenoid operative in the case where the door switch detects that the door is open. The main control unit also has a control function to continuously maintain the belt lock cancelling solenoid operative for a predetermined time even after the door is closed, that is, in the case where the door switch detects the door closing state after it detected the door opening state.
In a variation, the control apparatus also includes a door lock switch to detect the opening/closure of the door by sensing whether the door has been retained to the vehicle body, which switch is provided in a latch which retains the door to the vehicle body. The main control unit makes the belt lock cancelling solenoid operative only when both of the switches have sensed that the door is open.
In the invention, the door switch preferably comprises a normally closed type contact which is opened when the door is closed and is closed when the door is open, the door switch being connected to the belt lock cancelling solenoid and forming a part of a current supplying circuit of the solenoid.